Obesity and long-term survival after radical prostatectomy

Obesity is a modifiable risk factor associated with worse outcomes for many cancers, yet implications for prostate cancer are not well understood. Notably the impact of body mass index on long-term survival after treatment is unclear. We performed a retrospective cohort study on a large series of men who underwent radical prostatectomy to assess the impact of obesity on long-term biochemical recurrence-free survival, prostate cancer specific survival and overall survival.

Between 1982 and 2012, 11,152 men underwent radical prostatectomy at a single tertiary referral center. Patients were stratified according to body mass index as normal weight (body mass index less than 25 kg/m(2)), overweight (body mass index 25 to less than 30 kg/m(2)), mild obesity (body mass index 30 to less than 35 kg/m(2)) and moderate/severe obesity (body mass index 35 kg/m(2) or greater), comprising 27.6%, 56.0%, 14.1% and 2.3% of the cohort, respectively. Covariates included age, preoperative prostate specific antigen, surgery year, Gleason score, pathological stage, surgical margin and race. Predictors of biochemical recurrence-free survival, prostate cancer specific survival and overall survival were identified using Cox proportional hazard models.

Median followup was 5 years (range 1 to 27). Actuarial 20-year biochemical recurrence-free survival for mild and moderate/severe obesity was 65% and 51%, respectively, compared to 76% for normal weight men (p ≤0.001). In a multivariate model obesity was a significant predictor of biochemical recurrence-free survival (mild HR 1.30, p = 0.002; moderate/severe HR 1.45, p = 0.028) and overall survival (mild HR 1.41, p = 0.003; moderate/severe HR 1.81, p = 0.033). However, only mild obesity was significantly associated with prostate cancer specific survival (HR 1.51, p = 0.040), whereas moderate/severe obesity was not (HR 1.58, p = 0.356).

Obese men have higher rates of biochemical recurrence than normal weight patients during long-term followup. Obesity at the time of surgery independently predicts overall survival and biochemical recurrence-free survival but not prostate cancer specific survival.